| MEM Site Services Ltd | Construction | 2023 |
| Memari Ltd | Construction | 2025 |
| Membury Project Services Limited | Professional & scientific | 2019 |
| Memoir Ltd | Information & communication | 2021 |
| Memorial Court (Hanham) Management Company Limited | Households | 1995 |
| Memorial Woodlands Limited | Extraterritorial | 2013 |
| Memorial Woodlands U.K. Limited | Extraterritorial | 2019 |
| Memories by Angela Ltd | Administrative & support | 2019 |
| Memories by Tharcika Ltd | Extraterritorial | 2026 |
| Men's Cave Barber Limited | Other services | 2018 |
| Men's Cave II Limited | Other services | 2020 |
| MEN4REAL Ltd | Other services | 2021 |
| Mendable Worldwide Ltd | Information & communication | 2021 |
| Mendip & Bristol Consulting Limited | Professional & scientific | 2026 |
| Mendip and Somerset Homes Limited | Construction | 2021 |
| Mendip Batch Medical Limited | Financial services | 2014 |
| Mendip Botanicals Ltd | Manufacturing | 2024 |
| Mendip Building Limited | Construction | 2019 |
| Mendip Cleaning Services Limited | Administrative & support | 1986 |
| Mendip Conservatory Roofs Ltd | Construction | 2023 |
| Mendip Construction (Homes) Limited | Construction | 1997 |
| Mendip Electrical Contractors Limited | Construction | 2001 |
| Mendip Financial Services Limited | Financial services | 2007 |
| Mendip Funding Solutions Limited | Financial services | 2026 |
| Mendip Holdings Limited | Real estate | 2017 |
| Mendip Laser Combat Limited | Arts & recreation | 2014 |
| Mendip Meadows Developments Ltd | Construction | 2022 |
| Mendip Media Limited | Information & communication | 2005 |
| Mendip Media Productions Limited | Information & communication | 2020 |
| Mendip Motorhomes Ltd | Wholesale & retail | 2019 |
| Mendip Property Management Limited | Real estate | 2007 |
| Mendip Refrigeration Controls and Consultancy Services Limited | Professional & scientific | 2000 |
| Mendip Refrigeration Services Limited | Manufacturing | 1999 |
| Mendip Sauna Ltd | Health & social care | 2026 |
| Mendip Tiling Ltd | Construction | 2017 |
| Mendip Times Limited | Information & communication | 2005 |
| Mendip Toilet Hire Limited | Water & waste | 2011 |
| Mendip Travel Ltd | Extraterritorial | 2024 |
| Mendip Woodshavings Limited | Manufacturing | 2001 |
| Meng Fung Ltd | Wholesale & retail | 2020 |
| Meningitis Promotions Limited | Health & social care | 2002 |
| Meningitis Research Foundation | Health & social care | 2002 |
| Menlo Homes Ltd | Real estate | 2021 |
| Menobay Limited | Hospitality | 2016 |
| Menon Associates Limited | Professional & scientific | 2008 |
| Mensis Accountants Limited | Professional & scientific | 2020 |
| Mensis Professional Services Limited | Professional & scientific | 1999 |
| Mental Health Awareness Limited | Health & social care | 2021 |
| Mentor Communications Consultancy Limited | Information & communication | 1998 |
| Mentor UK Limited | Professional & scientific | 2005 |
| Mentora AI Limited | Information & communication | 2025 |
| Mentored Modular Ltd | Education | 2024 |
| Mentoring & Mindtherapy Ltd | Health & social care | 2023 |
| Mentovia Ltd | Health & social care | 2026 |
| Menzies Law Limited | Professional & scientific | 2009 |
| MEP Engineering Solutions Limited | Professional & scientific | 2010 |
| Meph Consulting Ltd | Other services | 2016 |
| Merak UK Holdings Limited | Financial services | 2022 |
| Meraki Publishing Limited | Information & communication | 2023 |
| Meraki Supplies Ltd | Wholesale & retail | 2019 |
| Mercanti Imports Limited | Wholesale & retail | 2016 |
| Mercanu Limited | Transport & logistics | 2018 |
| Mercenary Group Ltd | Construction | 2016 |
| Mercer & Co Investments Ltd | Real estate | 2022 |
| Mercer Kennedy Ltd | Financial services | 2025 |
| Mercers Properties Limited | Real estate | 2022 |
| Mercexecltd Ltd | Transport & logistics | 2025 |
| Merchandise From Africa Limited | Professional & scientific | 2022 |
| Merchant Arms Ltd | Administrative & support | 2014 |
| Merchant Bank Corp Partners Limited | Professional & scientific | 2005 |
| Merchant Finance London Limited | Financial services | 2017 |
| Merchant Optimisation Services Limited | Administrative & support | 2010 |
| Merchant Trade Software Limited | Information & communication | 2010 |
| Merchants Asset Management Limited | Professional & scientific | 2000 |
| Merchants Landing (Amenities) Limited | Households | 1984 |
| Merchants Rest Management Limited | Households | 2011 |
| Mercia Healthcare (Holdings) Limited | Construction | 1999 |
| Mercia Healthcare Limited | Construction | 1999 |
| Merclux Limited | Transport & logistics | 2016 |
| Mercury Car Repairs Ltd | Wholesale & retail | 2021 |
| Mercury Mortgages Ltd | Financial services | 2024 |
| Mercury Research UK Limited | Information & communication | 2018 |
| Mercy Creative Ltd | Professional & scientific | 2016 |
| Mercy Mercy Mercy Ltd | Hospitality | 2023 |
| Meredith Motocross Limited | Wholesale & retail | 2001 |
| Merediths Site Services Ltd | Mining & quarrying | 2019 |
| Mergapan Ltd | Wholesale & retail | 2025 |
| Mergapan Market Ltd | Wholesale & retail | 2021 |
| Mergerbill Limited | Households | 1980 |
| Meri Power Limited | Energy | 2010 |
| Meridan Financial LLP | | 2004 |
| Meridan Pension Services Limited | Financial services | 2010 |
| Meridian Building & Contractors Limited | Construction | 2026 |
| Meridian Building Developments Ltd | Construction | 2026 |
| Meridian Global Limited | Administrative & support | 2005 |
| Meridian Handpan Limited | Manufacturing | 2017 |
| Meridian Maritime Software Ltd | Information & communication | 2026 |
| Meridian Mortgage and Financial Services Limited | Financial services | 1999 |
| Meridian Tyre Repair Company Limited | Manufacturing | 1976 |
| Meril UK Limited | Wholesale & retail | 2019 |